Thallation of fluorenes: A kinetic and mechanistic study

The kinetics of thallation of fluorene with thallium triacetate (TTA) in HOAc‐H2SO4 solutions led to the rate expression \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm rate = [TTA]}^{\rm 2} [{\rm fluorene}] $$\end{document} The rate of thallation is found to increase with increasing acid concentration, and a sixth‐order dependence on [H2SO4] is observed. Decrease in solvent polarity increases the rate of thallation. The effect of substituents is in accord with the electrophilic substitution at an aromatic system. Thallation occurs at 4‐position. A mechanism similar to aromatic bromination is proposed for the thallation of fluorene.